In the conventional field of stereolithography and rapid prototyping apparatus, three-dimensional objects are build by layer-wise solidification of a material solidifyable under the action of electromagnetic radiation, commonly by photo-hardening of a photopolymer. There are methods and devices for the layered-wise construction of three-dimensional objects by exposure through an imaging unit comprising a predetermined number of discrete elements (pixels). Reference can be made, for example, to U.S. Pat. Nos. 5,247,180, 5,980,813, DE 93 19 405.5 U, DE 299 11 122 U, EP 1 250 995 A, EP 1 338 846 A, WO 01/00390, and WO 2005/110722.
With laser-based systems for photo-polymerisation, the energy or light output in the exposure point is provided by energy setting of the laser beam. To selectively harden a corresponding layer, the laser beam is scanned over the cross-sectional surface to be correspondingly hardened. The contours of the cross-sectional surface to be hardened can be scanned by the laser beam as a curve.
The layer-wise building of the three-dimensional object occurs by solidification in a cross-sectional area corresponding to a cross-section of a three-dimensional (3D) model corresponding to the three-dimensional object. Thus, the cross-sectional area to be hardened lies in the XY building plane and respective layers are hardened to a desired layer thickness in the Z dimension (Z direction). For execution of this building method, a process includes a step of slicing 3D model data (STL) into a group of sliced two-dimensional (2D) data to correspond to the cross-sectional area to be exposed. This prior art is illustrated schematically in FIG. 1.
The afore-mentioned prior art transformation of 3D model data to sliced, layered 2D data corresponding to respective cross-sectional areas, however, is complex and involve extensive algorithms and computer processing. Furthermore, accuracy of a layer-wise hardening of a photo-polymer depends on numerous factors, such as apportionment of the sliced cross-sections according to Z heights, setting of the contour lines of the sliced cross-sectional areas and a corresponding adjustment of an energy (light output) source and respective control elements, etc.